Seasonal hydrological dynamics govern lifestyle preference of aquatic antibiotic resistome

Antibiotic resistance genes (ARGs) are a well-known environmental concern. Yet, limited knowledge exists on the fate and transport of ARGs in deep freshwater reservoirs experiencing seasonal hydrological changes, especially in the context of particle-attached (PA) and free-living (FL) lifestyles. Here, the ARG profiles were examined using high-throughput quantitative PCR in PA and FL lifestyles during four seasons representing two hydrological phenomena (vertical mixing and thermal stratification) in the Shuikou Reservoir (SR), Southern China. The results indicated that seasonal hydrological dynamics were critical for influencing the ARGs in PA and FL and the transition of ARGs between the two lifestyles. ARG profiles both in PA and FL were likely to be shaped by horizontal gene transfer. However, they exhibited distinct responses to the physicochemical (e.g., nutrients and dissolved oxygen) changes under seasonal hydrological dynamics. The particle-association niche (PAN) index revealed 94 non-conservative ARGs (i.e., no preferences for PA and FL) and 23 and 16 conservative ARGs preferring PA and FL lifestyles, respectively. A sharp decline in conservative ARGs under stratified hydrologic suggested seasonal in-fluence on the ARGs transition between PA and FL lifestyles. Remarkably, the conservative ARGs (in PA or FL lifestyle) were more closely related to bacterial OTUs in their preferred lifestyle than their counter -parts, indicating lifestyle-dependent ARG enrichment. Altogether, these findings enhanced our under -standing of the ARG lifestyles and the role of seasonal hydrological changes in governing the ARG transition between the lifestyles in a typical deep freshwater ecosystem.(c) 2022 The Authors. Published by Elsevier B.V. on behalf of Chinese Society for Environmental Sciences, Harbin Institute of Technology, Chinese Research Academy of Environmental Sciences. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

In this study, the profiles of antibiotic resistance genes (ARGs) in particle-attached (PA) and free-living (FL) lifestyles were examined in the Shuikou Reservoir, Southern China. The results showed that seasonal hydrological dynamics played a critical role in shaping ARGs in PA and FL and in the transition of ARGs between the two lifestyles. Horizontal gene transfer was found to influence ARG profiles in both PA and FL, while they responded differently to the physicochemical changes under seasonal hydrological dynamics. The study also identified both non-conservative and conservative ARGs associated with PA and FL lifestyles.